Modern lightweight and durable articles require a variety of physical properties which frequently cannot be achieved with conventional coarse-grained metallic materials. Synthesis of fine-grained metallic materials using electrodeposition is described in the prior art. For structural applications these electroplated or electroformed parts require much greater thicknesses than used in coatings for wear, corrosion or aesthetic purposes, i.e., the required thickness of structural metallic layers range from 25 microns to 5 cm and, unlike prior art applications, the structural layers and coatings require weight and thickness tolerances not consistently achievable with conventional rack plating techniques where all parts to be plated are electrically connected in parallel. Unlike thin coatings, in these applications the weight of the electroplated material typically ranges from 5-100% of the total weight of the article.
As conventional rack and barrel plating, constituting “parallel plating” characterized by poor individual part thickness and weight control, does not provide sufficient part reproducibility and industrial settings do not permit plating one part at the time in a plating cell to achieve tight part weight and thickness specifications, plating methods are sought enabling the economic and simultaneous production of parts by a process which is readily scalable.
Methods for producing multiple parts in a single plating tank using DC are known.
Andricacos in U.S. Pat. No. 5,312,532 (1994) discloses a multi-compartment electroplating system for electroplating two or more disks simultaneously such that the electrodeposited material is substantially uniform in thickness and composition. Electroplating solution is circulated between a reservoir and a multi-compartment tank which has one cathode-paddle-anode (CPA) assembly for each compartment. Each CPA assembly has an anode, a cathode adapted for holding a wafer and employing a single thieving electrode which covers the entire floor of the compartment not covered by the wafer, and a paddle. Andricacos' plating process specifies the use of one power supply to provide current to every anode-cathode set and a second power supply to provide power to each anode and thieving electrode set.